1. Field of the Invention
The present invention relates to a collapsible container which includes a rectangular bottom wall and sidewalls pivotally joined to respective outer edges of the bottom wall and is changeable between an assembled state in which the sidewalls are raised from the bottom wall and a folded state in which the sidewalls are folded to be superimposed on the bottom wall.
2. Description of the Related Art
Sidewalls are individually formed in a collapsible container of the above-described type. Accordingly, the sidewalls are easier to bend as compared with noncollapsible containers comprising integrally formed sidewalls. When two or more collapsible containers are stuck onto another, one collapsible container falls into the other or another collapsible container, since a top opening of the collapsible container is spread. In particular, when a smaller container having the same length or width as the collapsible container is placed on the collapsible container, the smaller container often falls into the collapsible container.
In view of the above-described problem, one conventional collapsible container has projections formed on upper surfaces of sidewalls, and recesses are formed in the underside of the other or another container to be put onto the container with the projections. The projections and recesses are brought into a concavoconvex engagement so that the top opening of the collapsible container is prevented from spreading. See JP-A-2002-2696, for example.
In the above-described collapsible container, however, bringing the containers into a concavoconvex engagement is troublesome when the other or another container is put onto the collapsible container. Furthermore, recent collapsible containers tend to have sidewalls with reduced thicknesses in order to reduce the height of the sidewalls in a folded state. As a result, the upper container falls into the lower container during the piling work if displaced slightly by a thickness of the sidewall.